Smoke alarms and carbon monoxide alarms are typically mounted at various locations around a house or other buildings to detect dangerous air quality conditions that may arise as a result of fire and give an alarm signal. Such alarm units must be highly reliable so that the alarm can detect conditions invisible to the human senses when the occupants of the building are asleep. Domestic smoke alarms in the past have typically been powered by a battery that gave about one year of normal operation. No connection to the mains circuit was made. Recent changes to regulations in many countries have mandated the use of fixed wiring to provide mains power combined with battery back up for loss of mains power in smoke alarms.
Most mains power smoke alarms found in Australia, having battery back up systems, use a plug in connector with a small flexible cable (flex) that requires a further termination box for connection usually fixed above the ceiling. This arrangement is not desirable for the installer as he/she is required to fix the terminal connection means to a fixing point as is required by the wiring rules, this usually necessitates entering the roof cavity, plus the extra cost to purchase the junction box.
The small connector plug and separate terminal housing referred to above is used in many countries around the world. The problem with this method of termination is the requirement for a separate terminal connection means plus the plug can get knocked out of its connection when insulation batts or the like are pulled over the smoke alarm. The cable length may also not reach a fixing point for the terminal box. In this case the electrician has to make a fixing point closer to the smoke alarm.
Other smoke alarms in the market have integrated the terminals within their mounting plates, but with the addition of terminals and the conventional layout of components such as the battery position the alarm becomes large and bulky making it less commercially acceptable. Batteries also require replacement annually, hence a simple means is required to allow the battery replacement. The alarm must also prevent the user from connection to the mains circuit without the battery fitted. Many designs for battery removal are available on the market. Most have complicated door mechanism that hide the battery some have complicated switching that allow the user to keep the mains connection but isolate the sense electronics when the battery door is open. In most cases the battery is hidden and is difficult for impaired persons to remove or understand how removal is achieved.
It is an object of the invention to overcome at least some of the problems outlined above.